Any characteristic which is subject to
change and can have more than one
value such as age, intelligence,
motivation, gender, etc.
• Variable affected by the independent
• It responds to the independent variable.
• Variable that is presumed to influence
• It is the presumed cause, whereas the
dependent variable is the presumed
You are interested in “How stress affects
mental state of human beings?”
Independent variable ----- Stress
Dependent variable ---- mental state of human
You can directly manipulate stress levels in your
human subjects and measure how those stress
levels change mental state.
Other Names for Dependent and
It is a variable whose existence is inferred
but it cannot be measured.
Determining the effect of video clips on learning
ability of students of M.Phil.
The association between video clips and learning ability
needs to be explained.
Other variables intervene
Such as anxiety, fatigue, motivation, improper diet, etc.
It is caused by the independent variable and is
itself a cause of the dependent variable.
Higher education typically leads to
•Higher education----(independent variable)
•Higher income----(dependent variable)
•Better occupation---- intervening variable
It is causally affected by education and itself affects
Any characteristic of the research
participant/individual under study that
can be used for classification
Such as personal characteristics of gender,
height, weight, age, etc. in behavioral sciences.
• It is variable that is NOT allowed to be
changed unpredictably during an
• As they are ideally expected to remain the
same, they are also called constant variables.
An example of a constant variable is the voltage
from a power supply.
If you are examining “How electricity affects
experimental subjects” you should keep the
voltage constant, otherwise the energy supplied
will change as the voltage will be changed.
• Interval variables have a numerical value
• These have order and equal intervals.
• They allow not only to rank order the items that
are measured but also to quantify and compare
the magnitudes of differences between them.
Suppose you have a variable such as monthly
income that is measured in rupees, and we have
three people who make
• Rs. 15,000 and
A ratio variable is similar to an interval variable
with one difference: the ratio makes sense.
• Let’s say respondents were being surveyed about their
stress levels on a scale of 0-10.
• A respondent with a stress level of 10 should have
twice the stress experienced as a respondent who
selected a stress level of 5.
Age, height, and weight are also good examples of ratio
variables. Someone who is 6’.0” tall is twice as tall as
someone who is 3’.0” tall.
• They can be measured only in terms of whether the
individual items belong to certain distinct categories
• We cannot quantify or even rank/order the categories:
• Nominal data has no order
• One cannot perform arithmetic (+, -, /, *) or logical
operations (>, <, =) on the nominal data.
Marital Status: 1. Unmarried
• An ordinal variable is a nominal variable, but its different states
are ordered in a meaningful sequence.
• Ordinal data has order but the intervals between scale points may
• Because of lack of equal distances, arithmetic operations are
impossible, but logical operations can be performed on the
• A typical example of an ordinal variable is the socio-economic
status of families.
We know 'upper middle' is higher than 'middle' but we
cannot say 'how much higher'.
A questionnaire on the time involvement of scientists in the 'perception
and identification of research problems'.
The respondents were asked to indicate their involvement by selecting one
of the following codes:
1 = Very low or nil
2 = Low
3 = Medium
4 = Great
5 = Very great
Here, the variable 'Time Involvement' is an ordinal variable with 5 states.
A qualitative variable can be transformed into
quantitative variable(s), called dummy variable.
Preference variables are specific discrete variables whose values are
either in a decreasing or increasing order.
In a survey, a respondent may be asked to indicate the importance
of the following FIVE sources of information in his research and
development work, by using the code  for the most important
source and  for the least important source:
Multiple Response Variable
Multiple response variables are those which
can assume more than one value
A typical example is a survey questionnaire about the use of
computers in research.
The respondents were asked to indicate the purpose(s) for which they
use computers in their research work. The respondents could score
more than one category.
2.Lab automation/ process control
3.Data base management, storage and retrieval
4.Modeling and simulation
5.Scientific and engineering calculations
6.Computer aided design (CAD)
Extraneous variables are undesirable variables
that influence the relationship between the
variables an experimenter is examining.
An educational psychologist has developed a new learning
strategy and is interested in examining the effectiveness of this
The experimenter randomly assigns students into two groups. All of
the students study text materials on a biology topic for thirty
minutes. One group uses the new strategy and the other uses a
strategy of their choice.
Then all students complete a test over the materials.
Extraneous variable ------ pre-knowledge of the biology topic